All human hair goes through normal cycles of growth and rest. These phases are termed anagen, catagen, and telogen and they differ in length for different hair types. The growth phase, or anagen phase, in scalp hair lasts between two and eight years whereas the anagen phase in eyebrow hair lasts approximately four to seven months. Differences in the length of the anagen phase result in different hair lengths.
During the anagen phase, cell division at the base of the hair follicle adds cells to the hair shaft and results in hair growth. Hair grows approximately one centimeter, or half an inch, a month. Scalp hair can stay in this active phase of growth for up to seven years, but on average, lasts two to three years. The amount of time the hair follicle stays in the anagen phase is genetically determined.
The anagen phase is followed by a brief two to four week catagen phase or transitional phase. This is part of a renewal process wherein the scalp follicle is degraded and the hair stops growing but does not fall out. The hair follicle shrinks to about ⅙ of the normal length during the catagen phase and a “club hair” is formed.
The scalp follicle then goes into the telogen phase for two to four months. The telogen phase is also called the resting phase. During the telogen phase, the scalp hair still does not grow but remains attached to the follicle. Approximately ten to fifteen percent of all scalp hairs are in this phase at any one time. After the telogen phase, the cycle is complete and the hair follicle goes back into the anagen phase. Formation of the new hair shaft causes the old hair to be pushed out and lost. On average, 50-100 scalp hairs are lost due to this natural growth process every day.
Hair loss only becomes problematic when the rate of shedding exceeds the rate of regrowth or when new hair is thinner than the hair shed. A shift in the balance of hair loss and hair regrowth can be caused by many factors. Pattern baldness, or androgenetic alopecia, is likely caused by hereditary factors. Scarring on the scalp caused by inflammation can cause excessive hair loss as can poor nutrition, radiation, chemotherapy, medications, disease, hormonal changes, hair treatments, emotional distress, and sudden or excessive weight loss.
Treatments for baldness and excessive hair loss have been developed. Topical minoxidil and oral finasteride both treat male pattern baldness. A synthetic substance, anthralin, is also used by some doctors to treat cases of alopecia areata, a hair loss condition believed to be associated with autoimmune disease. Corticosteroids may also be injected into the scalp to treat certain types of excessive hair loss.
Despite the many advances in hair loss treatment, these prior treatments are either chemical or hormonal in nature. Adverse side effects such as severe allergic reactions, chest pain, unexplained weight gain, fainting, swollen hands and feet, decreased libido, and erectile dysfunction are associated with many of the hair loss treatments currently available. Accordingly, there remains a need for more natural and effective compositions for the treatment of hair loss.